This invention relates to test equipment, especially automated test equipment for testing and examining electronic devices such as integrated circuits.
Integrated circuits (xe2x80x9cICsxe2x80x9d) can be tested or/and examined in various ways. One testing/examining (diagnostic) technique is to electrically stimulate an IC and then monitor its electrical response, typically by comparing the actual response to a reference response. The stimulation/response-monitoring technique is commonly performed with automated test equipment connected to the external electrical leads, commonly referred to as pins, by which the IC interacts with the outside world. The test equipment stimulates the IC by providing electrical signals to the IC""s pins and then monitoring the resultant electrical signals provided from the IC on its pins.
Another diagnostic technique involves probing an IC, especially when the IC has failed and it is desirable to determine the reason(s) for failure. The probing technique can be done in an intrusive manner by physically contacting the IC with a probe. The probing technique can also be done in a largely non-intrusive manner by directing radiation such as light, electrons, or ions toward parts of the IC. The test equipment which performs the stimulation/response-monitoring technique often includes a probting capability.
FIG. 1 illustrates an example of a conventional test system that combines a stimulation/response-monitoring technique with a non-intrusive electron-beam probing capability for testing/examining an integrated circuit 10 referred to generally as a device under test (xe2x80x9cDUTxe2x80x9d). The test system in FIG. 1 consists of core automated test equipment 12, manipulator 14, test head 16, tester load board 18, interface module 20, device-side board (or card) 22, and device chamber 24 which contains an electron-beam probe (not separately shown). DUT 10 is situated in device chamber 24 and attached to device-side board 22 also situated in chamber 24.
An example of a test system containing automated test equipment 12, manipulator 14, and test head 16 is the Schlumberger ITS 9000(copyright) automated test system. An example of an electron-beam probe system containing device chamber 12 is the Schlumberger 10000(copyright) probe system. Module 20 interfaces between the probe and test systems. Inasmuch as electron-beam probing needs to be done in a high vacuum, interface module 20 is configured to be airtight along device-side board 22.
Interface module 20 consists of tester-side body 26, device-side body 28, and electrical interface conductors 30 which pass through openings (not shown here) in bodies 26 and 28 to connect tester board 18 to device-side board 22. Tester board 18, which electrically connects test head 16 to interface conductors 30 along tester-side body 26, is customized to match head 16. Different implementations of board 18 thereby permit interface module 20 to be utilized with different versions of head 16. In the large majority of state-of-the-art test systems that provide stimulation/response-monitoring capabilities, head 16 and board 18 have outer lateral peripheries that are approximately circular in shape. Device-side board 22 which connects interface conductors 30 to the pins of DUT 10, is similarly customized for testing DUT 10. Different versions of board 22 enable module 20 to be employed with different implementations of DUT 10.
During test operation, test equipment 12 generates electrical signals which are supplied through components 14, 16, 18, 20, and 22 to stimulate DUT 10. The resulting electrical response from DUT 10 is then furnished in the other direction through components 22, 20, 18, 16, and 14 to test equipment 12 for evaluation. The electron-beam probe in device chamber 24 non-intrusively probes DUT 10 to form an image of a portion of DUT 10. The probing may be done as test signals generated by equipment 12 are used to stimulate DUT 10.
One conventional example of interface module 20 suitable for interfacing an electron-beam probe system, such as the Schlumberger IDS 10000 probe system, to a test system, such as the Schlumberger ITS 9000 test system, which provides a stimulation/response-monitoring capability is the Schlumberger 768 pin interface load module. FIG. 2a perspectively illustrates the Schlumberger 768 pin load module. FIG. 2b depicts tester-side body 26 of the load module. FIG. 2c illustrates how the module connects tester board 18 to device-side board 22. FIG. 2c also depicts the generally circular outer lateral periphery of tester board 18.
Tester-side body 26 in the Schlumberger 768 pin load module contains four physically separate tester-side portions 32 having tester-side openings through which interface conductors 30 pass. The tester-side openings are arranged in a pattern whose outer periphery is shaped generally like a square. See FIG. 2b. Device-side body 28 similarly contains four physically separate device-side portions 34 having device-side openings through which conductors 30 also pass. As indicated in FIG. 2a, the device-side openings are arranged in a pattern whose outer periphery is likewise shaped generally like a square. Although difficult to see in FIGS. 2a and 2b, conductors 30 protrude sufficiently far out of these openings to contact electrical contacts, e.g., metal pads, on boards 18 and 22.
Each device-side portion 34 is situated largely opposite a corresponding one of tester-side portions 32 to form a combination that utilizes one quarter of the total number, i.e., 768 , of interface conductors 30 in the Schlumberger 768 pin load module. Each combination of one tester-side portion 32, corresponding device-side portion 34, and the associated quarter of interface conductors 30 can be removed as a unit from the Schlumberger 768 pin load module. This facilitates repairing the load module should one of these units fail. However, the module has only 768 conductors 30 and thus is limited to use in testing implementations of DUT 10 having no more than 768 pins.
ICs having more than 768 pins are being fabricated now and are expected to become more prevalent in the future. Accordingly, it is desirable to have a module which can accommodate considerably more than 768 pins as it interfaces between a non-intrusive probe system and an automated test system having a stimulation/response-monitoring capability. It is also desirable that such an interface module be easy to repair.
The present invention furnishes an interface module which, when installed in a test system, enables the system to test or/and examine an electronic device, typically an integrated circuit, having a large number of external electrical leads, e.g., pins. The module of the invention is suitable for interfacing between a state-of-the-art non-intrusive probe system and a state-of-the-art test system that provides a stimulation/response-monitoring capability and, when utilized in such an overall test system, can readily accommodate an IC having considerably more than 768 pins. The present interface module is also typically configured to facilitate module repair.
More particularly, an interface module in accordance with the invention is intended to be situated between (a) a test mechanism having multiple electrical tester contacts for carrying test signals and (b) a device-side board (or card) having multiple electrical device-side contacts for connection to external electrical leads of an electronic device, such as an IC, under test. The test signals may include power supply signals. The interface module contains a tester-side body, a device-side body, and a group of electrical interface conductors.
The tester-side body of the present interface module normally contains at least five physically separate generally wedge-shaped tester-side portions laterally arranged so that their tips are directed generally toward one another. The number of wedge-shaped tester-side portions is normally a multiple of four, eight being the lowest such multiple. Each tester-side portion has multiple tester-side openings suitable for being positioned opposite corresponding ones of the tester contacts of the test mechanism.
The device-side body of the interface module has multiple device-side openings suitable for being positioned opposite the device-side contacts of the device-side board. Each interface conductor extends through one of the tester-side openings and through a corresponding one of the device-side openings for connecting one of the tester-side contacts to a corresponding one of the device-side contacts.
The tester-side openings in the tester-side body are preferably arranged in a pattern whose outer periphery is shaped generally like a circle or a polygon having at least five sides. In the case of a polygon, each side of the polygon corresponds to a different one of the tester-side portions. Multiple ones of the tester-side openings in each tester-side portion define the corresponding side of the polygon. The polygon is typically a regular polygon, i.e., a polygon whose sides are of equal length and whose angles are of equal value.
As mentioned above, both the test head and the adjoining tester board in the large majority of state-of-the-art automated test systems which provide stimulation/response-monitoring capabilities have outer lateral peripheries of generally circular shape. As a result, the area available for tester-side openings in an interface module adjoining the tester board is typically approximately circular in shape. However, the outer periphery of the pattern of tester-side openings in the tester-side body of the conventional interface module described above in connection with FIGS. 2a-2c is generally square shaped. Hence, the tester-side body of the conventional interface module does not utilize all of the area available for tester-side openings in a test system where the part of the test system adjoining the tester-side body is generally circular in shape.
A regular polygon which has five or more sides and which is situated inside a given circular area so that the polygon""s sides all touch the periphery of the circular area occupies a greater fraction of the circular area than does a square situated in the circular area so that the square""s sides likewise all touch the periphery of the circular area. By arranging the tester-side openings in the tester-side body of the present interface module to be in a pattern whose outer periphery is shaped generally like a circle or a regular polygon having five or more sides, the tester-side body of the present module can readily utilize more of the normally circular area available for tester-side openings than does the tester-side body of the conventional interface module described above. Consequently, the tester-side body of the present interface module can readily have more, often considerably more, tester-side openings than the conventional interface module without increasing the areal density of the tester-side openings.
As also indicated above, each interface conductor in the present interface module passes through one of its device-side openings on the way to contacting one of the device-side contacts of the device-side board. Since the present module can have an increased number of tester-side openings relative to the conventional interface module described above, the device-side board can also have an increased number of device-side contacts. Accordingly, the interface module of the invention normally enables the test system to test/examine an electronic device having more external electrical leads than can be examined in a test system utilizing the conventional interface module.
The device-side body of the present interface module normally contains at least five physically separate device-side portions respectively corresponding to the tester-side portions of the tester-side body. Each device-side portion has multiple ones of the device-side openings. The interface module is arranged so that one of the interface conductors passes through one of the device-side openings of each device-side portion and then through one of the tester-side openings of the corresponding tester-side portion. Each tester-side portion, the corresponding device-side portion, and the associated interface conductors preferably form a unit which is removable from the interface module separately from each other such unit. This removability characteristic enables the module to be repaired easily.
The interface module of the invention can be modified in various ways. In one variation, the tester-side body can have as few as two physically separate tester-side portions which are laterally arranged so that their outer lateral peripheries are, as a group, shaped generally like a circle. The remainder of the interface module is arranged generally as described above except that the device-side body can similarly have as few as two physically separate device-side portions respectively corresponding to the tester-side portions. This variation enables the test system to test/examine an electronic device having an increased number of external electrical leads while still facilitating repair of the module.
The present invention also furnishes a test system for testing or/and examining an electronic device such as an IC. The test system contains a test mechanism, an interface module, and a device-side board all generally configured as specified above in connection with the present interface module. The test mechanism preferably includes a test head and a tester board attached to the test head. The tester board has the tester contacts which contact the interface conductors of the interface module. By customizing the test board to the characteristics of the test head, the interface module of the invention can be utilized with different versions of the test head.
The present test system normally includes a probe for probing the device under test in a largely non-intrusive manner. The probe is preferably positioned so as to probe the device under test from an opposite location to where the device-side board receives the device under test. In a preferred implementation, the device-side body of the interface module is physically coupled to the tester-side body substantially only through electrical interface conductors that pass through openings in the testers and device-side bodies. This largely isolates the probe from the test mechanism. Consequently, vibrations that may ccur in the test mechanism are largely prevented from being transmitted to the probe and disturbing its diagnostic function.